Update project files to use openbr C++ API

The C++ API defined in opengr_plugin.h is substantially more useful than
the c API, however to use it we need to link some QtLibraries (at least
Qt5Core.lib), and opnencv libraries as needed.
Also, need to include the relevant headers, and update include
directories.

OpenBR code is segregated in br_interface.cpp so that I can #undef min,
since well that is not exactly a harmless macro.

Project files were not updated in a general way (too many hardcoded
paths). Also, currently getting a heap corruption error that makes no
particular sense. Suspect I have an incompatible header/lib set
somewhere.